When bowhunters hunt game animals, they seek to hit their targets in such a manner that maximum trauma is inflicted upon their first shot (i.e., so that the first shot is a “killing shot”), since there may not be a chance for a second shot. In those cases where the first shot does not immediately critically wound and bring down the animal, it is at least desirable to have the arrow inflict sufficient trauma that heavy bleeding results, thereby resulting in relatively rapid death via loss of blood, as well as a blood trail which the hunter may follow to retrieve the animal. Otherwise, if the animal is only marginally injured, it may undergo prolonged suffering and may lack the ability to fend for itself in the wild—outcomes which most hunters and conservationists frown upon.
In order to maximize trauma, bowhunters often hunt game animals with broadhead-type arrowheads, that is, arrowheads which bear one or more blades extending laterally outwardly from the arrowhead and its trailing arrow shaft. This is in contrast to arrowheads used for recreational archery, which generally have a simple conical/pointed shape with no laterally-extending protrusions. The objective of a broadhead is to increase the effective area of the arrowhead which strikes the target animal, thereby enhancing the size of the inflicted wound and the lethality of the arrow.
However, broadheads suffer from the disadvantage that they are more likely to cause undesirable off-trajectory arrow flight than simple conical arrowheads. Since the blades extending outwardly from the broadhead effectively act as forward fletchings or “wings” on the arrow, even minor misalignments and/or other imperfections in one or more blades can cause an arrow to veer from its intended course. Additionally, the blades also make an arrow more susceptible to being blown off course by wind currents, since the blades can effectively define wind-catching “sails” on the broadhead.
As a result of the flight inaccuracies demonstrated by broadheads, the development of new broadheads has generally followed two paths. A first path involves “fixed-blade” broadheads, wherein the blades are immovably affixed to the arrowhead. These blades are usually designed to extend only a slight distance laterally outwardly from the arrowhead so as to reduce the aerodynamic effect of the blades. A second path involves “expandable” or “mechanical” broadheads, wherein movable blades affixed to the arrowhead are situated in a closed state close to the arrowhead and shaft when launched, but the blades subsequently move outwardly from the arrowhead during flight (preferably late in their flight) or upon striking a target. In the expandable/mechanical broadhead, the blades in their open state may extend further laterally outwardly from the arrowhead than in a fixed-blade broadhead because the blades, being closed for (preferably) most or all of the arrow flight, have lesser effect on arrow trajectory. Stated differently, by reducing the forwardly-facing blade surface area which is exposed during flight of the arrow, and then maximizing this area during or near impact, the expandable/mechanical broadhead seeks to avoid misflight while maximizing lethality.
Despite the foregoing, many prior expandable/mechanical broadheads carry their own unique disadvantages. Several expandable/mechanical broadheads operate by using restraining members (such as rubber O-rings) to hold their blades in place during flight, with the restraining member then being cut or otherwise ejected from the arrowhead at or near impact. The loss of the restraining member then allows the blades to spring open. Such broadheads are inconvenient and/or expensive to use because they require that a hunter obtain and carry a supply of restraining members—which are usually small in size, and easily lost—in order to make continued use of the broadheads in the field. In general, broadheads which do not require any O-rings or other sacrificial members are more conveniently used in the field.
Other expandable/mechanical broadheads require that the blades contact the target animal to open the blades. For example, several broadheads incorporate levers on the frontward/leading sides of the blades whereby the levers, upon contact with the target game, are to urge the blades into their open/unfolded state. Such broadheads can be problematic because some blades may contact the target, animal (and thereby open) before others, which can then cause the arrow to deviate from its intended trajectory. Additionally or alternatively, certain blades may open after entry rather than upon entry, thereby causing the entry wound size to be less than it would be had all blades been open upon entry. Further, some blades may be entirely prevented from opening if they are buried in tissue before their levers or other blade-triggering structures are subjected to sufficient opening force. Many of these broadhead designs also require that the levers or other blade-triggering structures be blunt, since a sharp triggering structure may simply penetrate the animal without encountering sufficient tissue resistance that it triggers the opening of the blade(s). These blunt structures can undesirably slow the arrow to such a degree that even if the blades open and a large entry wound is generated, it will not be sufficiently deep to lethally impair the animal.
More fundamentally, to expand on issues noted above, many expandable/mechanical broadheads suffer from the disadvantage that the blades are triggered to their open/unfolded state at a less than optimal time—either during flight, or after the blades have entered the animal. As previously noted, blades which are open during flight can cause undesirable arrow trajectory variations. As for blades which open after entry, while these may cause significant internal bleeding and other internal damage, the entry wound itself may be of small size, and it may be effectively “plugged” by the arrow shaft. The smaller entry wound (and the arrow stopping the wound) can inhibit blood loss and potentially allow the animal to flee for long distances before it expires.
Another problem experienced by some expandable/mechanical broadheads is the blades may be triggered to open/unfold upon impact and entry with a target animal, but they may then retract to their closed/folded state if the arrow is pulled rearwardly (i.e., the blades open when moving forwardly into a target, but then close when moving in reverse). Such broadheads can be advantageous insofar as they allow easier arrow removal by hunters, but they can be disadvantageous in that the arrows can more easily fall from, or be pulled from, the animal as it flees. An arrow that falls out may allow the animal to more readily bleed out, but it is usually desirable to have the arrow remain in place within the target animal because animals are generally less likely to flee (or to flee as far) when the arrow remains in place.
Another problem with many expandable/mechanical broadheads is their ease of preparation. As previously noted, some require the pre-firing installation of O-rings or other consumables to restrain the blades in a closed state until a time at or near impact, and the need to install such consumables can be inconvenient, particularly where a hunter has limited time to prepare an arrow for firing. Many broadheads also or alternatively require the user to grasp and manipulate the blades to place the broadhead in a firing condition, e.g., the user may need to grasp the blades and fold them into the closed state. These arrangements often result in finger cuts, which in turn cause difficulties with bow operation.